A system in which one board is conveyed from an upstream side to a downstream side via plural mounting device and components are mounted by the mounting apparatuses step by step has been widely used in a production factory to manufacture electric devices or the like. When mounting the components on the board conveyed via the mounting apparatus is completed, a mount state of the components is inspected before the board is carried out. In the inspecting process, the component is discriminated between a normal mount state in which components are accurately mounted with a predetermined posture at a predetermined location, and an abnormal mount state in which components are not mounted at the predetermined location or components are mounted with an abnormal posture. As a method of discriminating between these mount states, there is known a method of picking up previous and next images at a location where the component is mounted on a board, and comparing each data of the images to each other to inspect the mount state of the component (See Patent Document 1).
[Patent Document 1] JP-A-2002-271099